Conventional insulator materials for heat-resistant low-voltage automotive cables have a problem that sufficient heat resistance is not obtained unless a crosslinking treatment by electron beam irradiation is performed after extrusion molding of the coating layer and therefore, not only an expensive electron beam irradiation apparatus is necessary but also an electron beam irradiation step is required, resulting in low productivity.
In recent years, a resin composition for a non-crosslinked heat-resistant electric wire, using a polyphenylene ether material excellent in the heat resistance and the like, has been developed. The polyphenylene ether is excellent in the mechanical characteristics, electrical characteristics, heat resistance, low-temperature characteristics, low water absorption rate and dimensional stability but is poor in the molding processability, impact resistance and organic solvent resistance. Heretofore, it has been proposed to blend a polystyrene, a polyolefin, a hydrogenated block copolymer and the like with a polyphenylene ether and thereby improve impact resistance, molding processability and organic solvent resistance, which are problems for the polyphenylene ether (Patent Document 1).